It is now prevalent in satellite microwave communications systems for such systems to process multiple channels. This requires the combination or separation of the channels either for transmission or for processing after acquisition. This function is usually accomplished by means of a multiplexer.
The typical multiplexer consists of a series of input waveguides generally including filter elements connected to a waveguide manifold through ports or iris""Each of the filters is tuned and the iris"" designed for maximum efficiency of the overall system. The connections of the input waveguides to the manifolds must be accurately positioned according to strict spacing requirements governed by the wavelength (xcex) of the transmitted microwave energy. The spacing is measured along the longitudinal axis of the manifold from the shorted end.
The spacing requirements are often difficult to meet because of manufacturing tolerances. Prior art systems, however, provide no means by which spacing inaccuracies can be adjusted after the parts of the multiplexer are constructed and assembled. It is a purpose of this invention to provide a means to adjust the manifold spacing.
In order to obtain optimum performance of the multiplexer, while minimizing losses, the internal impedance of the various components must be closely matched. This process of tuning the system requires the balancing of hundreds of variables many of which are extremely sensitive because of the high frequency environment. The design of these components has, therefore, become a difficult technological challenge.
Although the optimization problem can be diminished through the use of various design techniques, precise construction of the components is made difficult, if not impossible by the inherent limitations of manufacturing tolerances. The design of the these components, therefore, ultimately relies on a trial and error process in which multiplexers are constructed, tested, modified, retested and gradually optimized. There are limits however, to the number of iterations which can be employed with constructive results.
It is therefore desirable to provide additional methods of tuning a manifold. It is therefore a purpose of this invention to provide a method of simulating manifold spacing adjustment by deforming the manifold dimensions to change the wavelength and assist in the tuning of the overall system.
The manifold of this invention is constructed with a primary manifold section to which the input wave guides, including filters, are connected. One end of the manifold is shorted and the other is open to form an output port. The filter couplings are spaced along the longitudinal axis of the manifold a predetermined distance from the shorted end of the manifold. A series of tuning brackets are mounted on the manifold at positions between the input waveguide/filter couplings. These brackets constrain the manifold and are constructed with adjustment screws extending through the brackets and mechanically connected to the manifold. The screws engage the bracket by means of threads to enable the screw to be adjusted in and out of the bracket. The movement of the adjustment screw will tend to deform the manifold dimensions resulting in a fine adjustment of the guide wavelength (xcex) of the multiplexer. In affect this change in the microwave characteristics of the manifold acts as a spatial adjustment of the position of the input wave guides.